The prior art most pertinent to the present invention deals with (1) cyanoacrylate-based absorbable tissue adhesives; (2) absorbable phosphate glasses; (3) resorbable calcium phosphate cement (CPC); and (4) polymeric methyl methacrylate/calcium phosphate-based composites. The absorbable cyanoacrylate-based tissue adhesives were disclosed by this inventor and coworkers in U.S. Pat. Nos. 5,350,798; 6,699,940; and 6,723,114, directed primarily to liquid systems of a methoxyalkyl cyanoacrylate containing a polymeric modifier to improve absorption and compliance of the cured adhesive. The adhesives were described as useful for soft tissue repair.
Also, pertinent to the present invention are the absorbable phosphate glasses which were disclosed by the present inventor and coworkers in U.S. Pat. No. 5,874,509, directed to surface-activated calcium phosphate glasses, preferably made using, in part, ZnO or SiO2, wherein surface activation entailed indirect grafting (through reactive intermediate functional groups) absorbable aliphatic polyester chains to provide improved adhesion to an absorbable polymeric matrix when used in forming absorbable phosphate thermoplastic composites.
A resorbable CPC composition was disclosed in U.S. Pat. No. 6,379,453 and was described as a self-setting inorganic bone cement. In spite of its ease of application, the CPC suffers from being fragile and highly susceptible to fracture under normal physiological stresses when used as a bone cement.
Also pertinent to the present invention are the polymeric methacrylate/calcium phosphate composites disclosed in U.S. Pat. No. 5,508,342 which deals with bioactive compositions and solid composites formed therefrom. These composites were noted as being able to provide sufficient sustained and timed release levels of Ca+2 and (PO4)−3 ions which can provide long-term protection against demineralization and promote mineralization of contiguous skeletal tissue. Accordingly, such composites were expected to have wide application as prophylactic, adhesive, prosthetic, and restorative materials, particularly in the field of dentistry.
Unfortunately, the prior art described above failed to identify an absorbable composite that has the integrated attributes of the (1) absorbable cyanoacrylate tissue adhesives, (2) high modulus phosphate-based microparticles as fillers in a thermoplastic matrix, and (3) absorbable phosphate glasses and their use as soluble or partially soluble calcium phosphate-based microparticles, capable of the controlled release of bioactive ions needed for bone mineralization, namely, (PO4)−3 and Ca+2. The perceived clinical significance of these integrated attributes provided an incentive to pursue the present invention which deals with a new type of self-setting absorbable, bioactive, polymeric, cyanoacrylate composite based on flowable precursors comprising water-soluble or partially water-soluble calcium-phosphate solid microparticulates in a liquid cyanoacrylate-based matrix.